Antimicrophonic &#34;v&#34; tension rod



May 9, 1950 P. H. SASSAMAN E L ANTIMICROPHONIC "v" TENSION ROD Filed Dec. 24, 1948 n 5/8 UEIEU I l l I'I'ISETI ll KIWI 3 Wm# m w 9 a 2. 0 M M P my Patented May 9, 1950 UNITED STTE PTELNT QFFICE ANTIMICROIHONIC "w TENSION ROD Application December 24, 1948, Serial No. 67,154

7 Claims.

The present invention relates to electron discharge devices and more particularly to a means for mounting vibration free filamentary cathodes in such devices. The usual electrodes assembly of electron discharge devices includes more or less concentric anode grid and cathode electrodes supported in position between parallel insulating spacers. In the case of filamentary electron discharge devices, the filamentary cathode ordinarily passes through holes in the spacers at or near the axis of the tube, and means are provided for applying a tension to the filament so that it lies in a substantially straight line between the two spacers and under some degree of tension. One end of the filament is ordinarily directly secured to a lead-in conductor, while the other end is connected to a spring tension support and thus to another lead-in conductor which may pass through the spacers near their edge. It is desirable to provide a tension on the filament which may readily be adjusted to a constant value as between successive tubes, so that the relationship of the filament to the other electrodes of the discharge device is maintained constant. If the tension is insufficient nonuniformity in operation of the discharge devices may result due to improper spacing and sagging of the filamentary cathode. Jars and vibration of the discharge devices tend to produce vibration of the cathode, with consequent interference with normal operation. Furthermore, vibration of the filamentary cathode tends to cause a sliding motion of the filament wire against the edge of the aperture in the spacer members, thus either sawing the hole larger which allows displacement of the filamentary cathode, or weakening the cathode so that it is readily fractured. It has been discovered that lateral vibration of the spring tension device is particularly liable to wire breakage of the filament. Thus, it is particularly important to prevent any lateral vibration of the filament and especially of the filament tensioning means. Still, the tensioning means should not be so complicated in construction so as to make assembly difiicult or such as to unduly increase the cost of manufacture of the tube. Also, the tensioning device must be Finally, the tensioning device must be capable of being easily adjusted to give maximum tensions.

An object of the present invention is the provision of a suspension for filamentary cathodes whereby said cathodes are maintained in fixed position.

Another object of the present invention is the provision of a resilient suspension for filamentary cathodes which inherently is resistant to lateral vibration.

Another object of the present invention is the provision of a tensioning arrangement for filamentary cathodes which results in a much lower microphonic level for the tube in which it is ,placed than presently known constructions.

, is the provision of a filament tensioning construction which may readily be adjusted by factory operators and which will not involve additional difficulty in mounting the device.

The foregoing objects and results are attained in accordance with an aspect of the present invention by providing a top filament tensioning arrangement in the form of a generally U or V shaped tension rod of comparatively small transverse dimensions, having the top filament tab connected to the tension wire at somewhere near its mid-point. The ends of the tension wire are welded otherwise secured to tabs on a transverse fixed support over the top spacer mica. By varying the amount of bend in the tabs the amount of tension applied to the filament may very accurately be adjusted. Also by limiting the diameter of the tension rod to a certain range 01' sizes which has been found to work well, the maximum operating range of the tension arrangement may be increased such that a reasonable elongation of the filament does not lessen the amount of tension to a marked degree. The present invention will bemore fully understood by reference to the following detailed description which is accompanied by a drawing in which Fig. 1 shows, in an elevational view, an electron discharge device embodying the principles of the present invention, while end of the filamentary cathode vice.

: rangement generally 4 for the tube.

.ment' shown in elevation'in Fig. 1. figure it will be seen that support'rod '36 passing Fig. 2 is a perspective View of a filament tension hook according to principles of the present invention.

In Fig. 1 there is shown an electron discharge device generally indicated by reference character ii]. The device may include within an evacuated casing 2 a mount assembly I4. The particular tube shown here'includes in mount I4 a filamentary cathode l6, and surrounding the cathode a grid l8 and an anode 20. Grid [8 and i anode 20 are maintained in position by insulat ing spacers 22 and 24. While-notso 'shown'in this figure, it is customary to provide apertures in the spacers 22 and 24'through which extensions of the side rods of gridilB and tabs'on anode 20 pass, whereby the assembly is maintained in its operative arrangement. The filamentary cathode passes through small. holesat.

about the axis of thetube. One of the holes is indicated by reference character 26 and is preferably triangular inform as shown in Fig.2'with one apex at the axis of the mount. The lower I5 is secured through tab 28 to a support 39 attached to a lead-through electrode 3! which extends through the glass header of the tube and forms a connection pin on the exterior of the discharge de- The other end of the filament is connected through tab 32 to a tension spring arindicated by character 34 which is supported on the upper end of support'rod 36. The lower end of support rod 3 5 is connected to another lead-through electrode 38 which passes through the header of the tube to form a second plug-in connection pin The grid and anode of the'triode structure are also connected to other leadthrough electrodes which are not specifically identified as they, are not concerned with the present invention.

While our invention is not limited thereto, we

' have chosen to illustrate in Fig. 1 the application of our invention to a tube having. a lock-in type of plug-in base wherein the lead-through conductors 3! and 38 actually form connection pins at the bottom end of the tube. Also, the

ment beneath spacer 24, butv since thisarrangement is not part of the present invention it will not be further described'here.

InFig. 2 we have shown in greatly enlarged perspective view the filamenttensioning arrange- Fkom this through the upper spacer 22 has securedthereto a short L-shaped member 40, carryingartransverse member 42 having along its upper edge a pair of tabs or lugs 44 and 46. Lying across the upper surface of bent-over connection tabs 44 and 46 are the two ends of tension rod 34. The

rod is preferably bent into a. generally U or V shaped formation. Near the free endsof rod 34 they are secured to the tabs.44 and 46, for example, by spot welding. Filament 16 has secured' to its upper end a folded over connection tab 32.

of-.between. four and one-half and live thousandths of an inch,.and if its width, that-is the distance between tabs 44 and 46, is fairly large reference compared to the distance between member 42 and tab 32, thus forming a short V. With a short substantially equilateral V, we have discovered that the point of attachment of tab 32 to tension wire 34 is not particularly critical. It need not be exactly at the apex, nor need tension wire 34 be formed into a sharp pointed V, but a bowed formation is all that is necessary. Nor is it necessary for wire [6 to fall directly into one of the corners of the triangular hole 26. Its position is maintained very well even though it is originally placed'so that it lies somewhere along the middle of one of the sides of the triangle.

Tests indicate that a top tension arrangement as. shown in Fig. 2 produces a tube with a lower microphonic level than could be obtained with other tensioning arrangements of which we are aware, plus the use of grid dampeners, that is insulated members secured to the grid support rod, and bearing against the filament somewhere A "filamentwire '18 than would be possible with a heavier tension rod, because there is much less possibility of putting a permanent set in the wire 34, when-the preferred relationship of diameter and length is used. It is believed also that the excellent performance of the present invention with regard/to microphonic tendencies of the tube may. be'predicated on the fact that the top of the'filament is supported from vibrating in a lateral direction by the two arms of the tension rod forming'a comparatively obtuse angle with one another. Also, since tension rod 34 is comparatively light, microphonism can not be initiated or sustained by reason of the vibration of the toptab and the weight of the resilient mounting means. The tension applied by tension spring or rod 34 may be adjusted accurately were substantial range of.va1uesby bending lugs 44 and 46 downward toward plate 42. Also, it should be noted that'since the welds between tabs 44 and 46 and wire 34 is made near the extreme ends of wire 34.. any weakening of the wire 34 caused bythe'welds does not extend to the region of the wire .where the maximum bending takes place.

While we have shown and particularly described an embodiment of the present invention, it-sbould. be clearly understood that it is not limited thereto, but that modifications within the scope-thereof may be made.

What we claim is:

l.- Inan electric discharge device having a filament with connector tabs at its ends, means for supporting said filament including a fixed support adjacent one end of said filament, a support carrying a-transverse member having a number of bent over lug portions directed away from said filament. andv a spring member having a bend intermediate its and its ends secured to said lugsand means for securing one of said connectortabs tosaid spring intermediate its ends, said spring member lying across the bends in said lugs.

2. In an electric discharge device having a filament with connector tabs at its ends, a support carrying a transverse member having a number of bent over lugportions directed away from said filament, and .a spring member having a bend intermediate its ends, and its ends secured to the ends of said lubs, and means for securing'one of "said'connector tabs to said spring intermediate its ends, said spring member crossing the bends in said lugs.

3. A tension device for use in electron discharge devices including a resilient rod-like member having a bend intermediate its ends, a transverse member having bent-over lugs to which the ends of said rod-like members are attached, said rod lying across the bends in said lugs.

4. A tension device for use in electron discharge devices including a resilient rod-like member having a bend intermediate its ends, a transverse member having bent-over lugs to which the ends of said rod-like members are attached, said rod lying across the bends in said lugs, the length of each of the legs of said rod being substantially equal to the length of said transverse member.

5. A tension device for use in electron discharge devices including a resilient rod-like member having a bend intermediate its ends, means for securing an end of a filament to said bend, a

transverse member having bent-over lugs to which the ends of said rod-like member are attached said lugs being directed away from said filament.

6. A tension device for use in electron discharge devices including a resilient rod-like member having a bend intermediate its ends, means for securing an end of a filament to said bend, a transverse member having bent-over lugs to which the ends of said rod-like member are attached, said rod lying across the bends in said lugs said lugs being directed away from the bend in said rod-like member.

7. A tension device for use in electron discharge devices including a resilient rod-like memher having a bend intermediate its ends, means for securing an end of a filament to said bend, a transverse member having bent-over lugs to which the ends of said rod-like member are attached, said rod lying across the bends in said lugs, the length of each of the legs of said rod being substantially equal to the length of said transverse member.

PAUL H. SASSAMAN. DONALD R. KERSTETTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,298,929 Dailey Oct. 13, 1942 FOREIGN PATENTS Number Country Date 526,554 Germany Dec. 16, 1928 

